Substituent effects on indium-phosphorus bonding in (4-RC6H 4S)3In·PR′3 adducts (R = H, Me, F; R′ = Et, Cy, Ph): A spectroscopic, structural, and thermal decomposition study

Article abstract of DOI:10.1021/ic051138r

The tris(arylthiolate)indium(III) complexes (4-RC₆H ₄S)₃In [R = H (5), Me (6), F (7)] were prepared from the 2:3 reaction of elemental indium and the corresponding aryl disulfide in methanol. Reaction of 5-7 with 2 equiv of the appropriate triorganylphosphine in benzene or toluene resulted in isolation of the indium-phosphine adduct series (4-RC₆H₄S)₃In·PR′₃ [R = H, R′ = Et (5a), Cy (5b), Ph (5c); R = Me, R′ = Et (6a), Cy (6b), Ph (6c); R = F, R′ = Et (7a), Cy (7b), Ph (7c)]. These compounds were characterized via elemental analysis, FT-IR, FT-Raman, solution ¹H, ¹³C{¹H}, ³¹P{¹H}, and ¹⁹F (7a-c) NMR spectroscopy, and X-ray crystallography (5c, 6a, 6c, and 7a). NMR spectra show retention of the In-P bond in benzene-d₆ solution, with phosphine ³¹P{¹H} signals shifted downfield compared to the uncoordinated ligand. The X-ray structures show monomeric 1:1 adduct complexes in all cases. The In-P bond distance [2.5863(5)-2.6493(12) A] is influenced significantly by the phosphine substituents but is unaffected by the substituted phenylthiolate ligand. Relatively low melting points (88-130°C) are observed for all adducts, while high-temperature thermal decomposition is observed for the indium thiolate reactants 5-7. DSC/TGA and EI-MS data show a two-step thermal decomposition process, involving an initial loss of the phosphine moiety followed by loss of thiolate ligand.

Full text of DOI:10.1021/ic051138r

Inorg. Chem. 2005, 44, 9914−9920
Substituent Effects on Indium Phosphorus Bonding in
−
(4-RC6H4S)3In PR Adducts (R ) H, Me, F; R′ ) Et, Cy, Ph): A
‚
′
3
Spectroscopic, Structural, and Thermal Decomposition Study
Glen G. Briand,* Reagan J. Davidson, and Andreas Decken
Department of Chemistry, Mount Allison UniVersity, SackVille, New Brunswick, Canada E4L 1G8,
and Department of Chemistry, UniVersity of New Brunswick, Fredericton,
New Brunswick Canada E3B 6E2
Received July 8, 2005
The tris(arylthiolate)indium(III) complexes (4-RC6H4S)3In [R
reaction of elemental indium and the corresponding aryl disulfide in methanol. Reaction of 5
appropriate triorganylphosphine in benzene or toluene resulted in isolation of the indium phosphine adduct series
(4-RC6H4S)3In PR [R H, R′ ) Et (5a), Cy (5b), Ph (5c); R Me, R′ ) Et (6a), Cy (6b), Ph (6c); R F, R
Et (7a), Cy (7b), Ph (7c)]. These compounds were characterized via elemental analysis, FT-IR, FT-Raman,
)
H (5), Me (6), F (7)] were prepared from the 2:3
−7 with 2 equiv of the
−
‚
′
)
)
)
′
3
)
solution H, 13C
NMR spectra show retention of the In
downfield compared to the uncoordinated ligand. The X-ray structures show monomeric 1:1 adduct complexes in
all cases. The In P bond distance [2.5863(5) 2.6493(12) Å] is influenced significantly by the phosphine substituents
but is unaffected by the substituted phenylthiolate ligand. Relatively low melting points (88 130 C) are observed
for all adducts, while high-temperature thermal decomposition is observed for the indium thiolate reactants 5 7.
{
1H
}
,
31P
{
1H
}
, and 19F (7a
−
c) NMR spectroscopy, and X-ray crystallography (5c, 6a, 6c, and 7a).
1
−
P bond in benzene-d6 solution, with phosphine 31P
{ }
1H
signals shifted
−
−
−
°
−
DSC/TGA and EI-MS data show a two-step thermal decomposition process, involving an initial loss of the phosphine
moiety followed by loss of thiolate ligand.
Introduction
Despite their potential utility, there has been an absence
of systematic studies in the literature that examine the effect
of the substituent variation on the bonding and physical (e.g.,
thermal stability) properties of indium-phosphine adducts.
Compounds of the type (RS)3In‚PR′3 are ideal candidates
for these investigations, as the requisite homoleptic alkyl-
and arylindium thiolates (RS)3In [R ) Et; i-Pr; n-Bu; t-Bu;
C5H11; Ph; C6F5; 2-MeC6H4; 2,4,6-(CF3)C6H2; 2,4,6-t-
Bu3C6H2; C10H7] have been prepared in high yield via
metathesis,4,5 redox,6,7 or electrochemical8 routes. However,
the alkyl- and unsubstituted phenylthiolate derivatives have
Trialkyl indium compounds have been of considerable
interest in recent years as reactants for the metal-organic
chemical vapor deposition (MOCVD) of III-V semiconduc-
tor materials.1 In particular, 1:1 adducts with tertiary phos-
phines have been studied as potential single-source precursors
to indium phosphide (InP).2 Complexes which incorporate
both elements connected by a chemical bond may provide
improved processes for the preparation of thin films due to
the controlled stoichiometric introduction of the elements,
simplified fabrication equipment, and deposition of desired
phases at lower temperatures compared to multisource
processes.3
(2) (a) Visona, P.; Benetollo, F.; Rossetto, G.; Zanella, P.; Traldi, P. J.
Organomet. Chem. 1996, 511, 59-65. (b) Bradley, D. C.; Chudzynska,
H.; Faktor, M. M.; Frigo, D. M.; Hursthouse M. B.; Hussain, B.; Smith,
L. M. Polyhedron 1988, 7, 1289-1298. (c) Wells, R. L.; Baldwin, R.
A. Organometallics 1995, 14, 2123-2126. (d) Self, M. F.; McPhail,
A. T.; Jones, L. J., III; Wells, R. L. Polyhedron 1994, 13, 625-634.
(e) Beachley, O. T.; Banks, M. A.; Churchill, M. R.; Feighery, W.
G.; Fettinger, J. C. Organometallics 1991, 10, 3036-3040.
(3) Gysling, H. J.; Wernberg, A. A. Chem. Mater. 1992, 4, 900-905.
(4) (a) Chadha, R. K.; Hayes, P. C.; Mabrouk, H. E.; Tuck, D. G. Can.
J. Chem. 1987, 65, 804-808. (b) Suh, S.; Hoffman, D. M. Inorg.
Chem. 1998, 37, 5823-5826.
* To whom correspondence should be addressed. Tel: (506) 364-2346.
Fax: (506) 364-2313. E-mail: gbriand@mta.ca.
(1) (a) Knauf, J.; Schmitz, D.; Strauch, G.; Ju¨rgensen, H.; Heyen, M.;
Melas, A. J. Cryst. Growth 1988, 93, 34-40. (b) Wang, T. Y.; Welch,
D. F.; Schifres, D. R.; Treat, D. W.; Bringans, R. D.; Street, R. A.;
Anderson, G. B. Appl. Phys. Lett. 1992, 60, 1007-1009. (c) Fry, K.
L.; Kuo, C. P.; Larsen, C. A.; Cohen, R. M.; Stringfellow, G. B. J.
Electron. Mater. 1986, 15, 91. (d) Ogasawara, M.; Kamada, H.;
Imamura, Y. J. Cryst. Growth 1991, 115, 254-260.
9914 Inorganic Chemistry, Vol. 44, No. 26, 2005
10.1021/ic051138r CCC: $30.25
© 2005 American Chemical Society
Published on Web 11/15/2005

Substituent Effects on Indium-Phosphorus Bonding
not been structurally characterized due to limited solubility
in organic solvents. This is presumably a result of extensive
intermolecular In‚‚‚S interactions and polymeric structures
in the solid state.4,6 The introduction of sterically encumbered
arylthiolate ligands has facilitated an increased solubility and
the structural characterization of the monomeric species
(2,4,6-t-Bu3C6H2S)3In (1), which exhibits a distorted trigonal
planar geometry at indium.5a The Lewis acidic nature of
(RS)3In species has also allowed for the isolation of
monomeric 1:1 [(t-BuS)3In(py) (2)4b] and 1:2 [(PhS)3In(py)2
(3),6 (i-PrS)3In(dmap)2 (4)4b] adducts [py ) pyridine, dmap
) 4-(dimethylamino)pyridine] from reactions with excess
amine ligand. Structural investigations show the former to
display distorted tetrahedral geometries at indium in the solid
state, while the latter exhibit trigonal bipyramidal coordina-
tion environments, with the amine nitrogen atoms occupying
axial positions. Interestingly, the formation of both 1:1 (2)
and 1:2 (3) adducts from excess pyridine suggests a varying
Lewis acidity for indium, which is presumably an effect of
altering the thiolate ligand.
Extensive studies into phosphine adducts of the related
indium(III) halides have yielded similar 1:19,10 and 1:2,10,11
complexes, while 1:3 adducts have only been characterized
spectroscopically.10g With regard to indium thiolate-phos-
phine adducts, only the 1:1 complex (PhS)3In‚PCy3 (5b) has
been structurally characterized and was prepared in moderate
yield from the reaction of the 1:2 hydride intermediate H3-
In‚(PCy3)2 with Ph2S2.12 Although little physical data were
reported, the monomeric structure and relatively low melting
point of 5b suggest potential for the preparation of volatile
indium thiolate-phosphine complexes, prerequisite for
MOCVD materials. In this context, we report the facile
synthesis of a series of 1:1 indium thiolate-phosphine
adducts (4-RC6H4S)In‚PR′3 [R ) H, R′ ) Et (5a), Cy (5b),
Ph (5c); R ) Me, R′ ) Et (6a), Cy (6b), Ph (6c); R ) F, R′
) Et (7a), Cy (7b), Ph (7c)], and the effect of the thiolate
and phosphine substituents on the spectroscopic and struc-
tural characteristics, as well as the thermal decomposition
properties, of these compounds.
Experimental Section
General Considerations. Melting points were recorded on an
Electrothermal MEL-TEMP melting point apparatus and are uncor-
rected. Infrared spectra were recorded as Nujol mulls on a Mattson
Genesis II FT-IR spectrometer in the range 4000-400 cm-1. FT-
Ramam spectra were obtained on a Bruker RFS 100 spectrometer.
Solution 1H, 13C{1H}, 19F, and 31P{1H} NMR spectra were recorded
at 23 °C on a JEOL GMX 270 MHz spectrometer (270.2, 67.9,
254.2, and 109.4 MHz, respectively) or a Varian Mercury 200
MHz+ spectrometer (200.0, 50.3, 188.2, and 81.0 MHz, respec-
tively) and are calibrated to the residual solvent signal. Elemental
analyses were provided by Chemisar Laboratories, Inc., Guelph,
Ontario, Canada.
Differential scanning calorimetry (DSC) and thermogravimetric
analysis (TGA) data were collected simultaneously on a TA
Instruments SDT Q600. Samples were held at 30 °C for 5 min,
then heated at a rate of 10 °C/min to 600 °C. All analyses were
carried out in aluminum sample cups under dinitrogen atmosphere.
Electron impact mass spectrometry (EI-MS) data were collected
after direct insertion of the solid sample from a 1177 injection port
on the Varian 3800 GC using a Varian Saturn MS/MS. An initial
temperature of 40 °C was held for 3 min, ramped at a rate of 20
°C/min to 300 °C, and held for 4 min for a total of 20 min. Spectra
were collected in the range of m/z 50-650.
Synthetic Procedures. Benzenethiol 97%, 4-methylbenzenethiol
98%, 4-fluorobenzenethiol 98%, triphenylphosphine 99%, trieth-
ylphosphine 99%, tricyclohexylphosphine, indium powder 99.99%,
methanol anhydrous 99.8%, toluene anhydrous 99.8%, benzene
anhydrous 99.8%, and hexane anhydrous 95+% were used as
received from Aldrich. Hydrogen peroxide 30% solution was used
as received from ACP.
Aryl disulfides (4-RC6H4S)2 were prepared from reaction of the
appropriate arylthiol ligand (5.51 mmol) with a 30% hydrogen
peroxide solution (0.25 g, 7.35 mmol) in methanol (5 mL; R ) H,
Me) or water (5 mL; R ) F). The reaction mixture was stirred for
3 h then allowed to evaporate slowly at 23 °C to yield colorless
crystals. After 1 day, the reaction mixture was filtered, washed with
MeOH (5 mL), and dried in vacuo to yield the aryl disulfide as
colorless crystals (81-95%).
(5) (a) Ruhlandt-Senge, K.; Power, P. P. Inorg. Chem. 1993, 32, 3478-
3481. (b) Bertel, N.; Noltemeyer, M.; Roesky, H. W. Z. Anorg. Allg.
Chem. 1990, 588, 102-108. (c) Nomura, R. Inazawa, S.; Kanaya,
K.; Matsuda, H. Polyhedron 1989, 8, 763-767.
(6) Annan, T. A.; Kumar, R.; Mabrouk, H. E.; Tuck, D. G. Polyhedron
1989, 8, 865-871.
(7) Kumar, R.; Mabrouk, H. E.; Tuck, D. G. J. Chem. Soc., Dalton Trans.
1988, 1045-1047.
(8) Green, J. H.; Kumar, R.; Seudeal, N.; Tuck, D. G. Inorg. Chem. 1989,
28, 123-127.
(9) Alcock, N. W.; Degnan, I. A.; Howarth, O. W.; Wallbridge, G. H. J.
Chem. Soc., Dalton Trans. 1992, 2775-2780.
The compounds described herein were prepared by general
procedures as indicated below. Specific details regarding reactant
quantities and product isolation are presented in Table 1. The
preparation of (C6H5S)3In (5) is a modification of a previously
reported procedure.7 All reactions were carried out under nitrogen
atmosphere using standard Schlenk techniques.
Preparation of (4-RC6H4S)3In [R ) H (5), Me (6), F (7)]. A
solution of (4-RC6H4S)2 in methanol (5 mL) was added dropwise
to a slurry of indium powder in methanol (5 mL) at 23 °C and
heated under reflux for 3 h. After cooling to 23 °C, the reaction
was filtered to remove a white precipitate. The residual solvent
removed under vacuum to yield a white powder of 5-7.
(10) (a) Brown, M. A.; Tuck, D. G.; Wells, E. J. Can. J. Chem. 1996, 74,
1535-1549. (b) Baker, L.-J.; Kloo, L. A.; Rickard, C. E. F.; Taylor,
M. J. J. Organomet. Chem. 1997, 545-546, 249-255. (c) Godfrey,
S. M.; Kelly, K. J.; Kramkowski, P.; McAuliffe, C. A.; Pritchard, R.
G. Chem. Commun. 1997, 1001-1002. (d) Carty, A. J.; Tuck, D. G.
J. Chem. Soc. A 1996, 1081-1087. (e) Carty, A. J. Can. J. Chem.
1967, 45, 345-351. (f) Carty, A. J.; Tuck, D. G. Prog. Inorg. Chem.
1975, 19, 243. (g) Carty, A. J.; Hinsberger, T.; Boorman, P. M. Can.
J. Chem. 1970, 48, 1959-1970.
(11) (a) Degnan, I. A.; Alcock, N. W.; Roe, S. M.; Wallbridge, M. G. H.
Acta Crystallogr. C 1992, 48, 995-999. (b) Veidis, M. V.; Palenik,
G. J. Chem. Commun. 1969, 586-587.
(12) Cole M. L.; Hibbs D. E.; Jones C.; Smithies N. A. J. Chem. Soc.,
Dalton Trans. 2000, 545-550.
Inorganic Chemistry, Vol. 44, No. 26, 2005 9915

Briand et al.
Table 1. Reaction Conditions, Yields, Elemental Analyses, and Melting Points
reagents
(g, mmol)
yield
(g, mmol, %)
elemental analysis
[% calcd (found)]a
mp
(°C)
compound
isolation conditions
pumped to dryness
5
In(0.25, 2.1)
(C6H5S)2 (0.70, 3.3)
In(0.25, 2.1)
(4-MeC6H4)2S2 (0.80, 3.3)
In (0.25, 2.1)
(4-FC6H4)2S2 (0.83, 3.3)
PEt3 (0.11, 0.90)
(C6H5S)3In (0.20, 0.45)
toluene
0.44, 2.0, 95
0.48, 1.9, 90
0.45, 1.8, 82
0.16, 0.28, 63
C: [48.87 (48.46)]
H: [3.42 (2.96)]
C: [52.06 (51.97)]
H: [4.38 (4.22)]
C: [43.56 (43.25)]
H: [2.44 (2.06)]
C: [51.52 (51.93)]
H: [5.54 (5.93)]
208 (dec)
210 (dec)
220 (dec)
103
6
pumped to dryness
pumped to dryness
1 day at 23 °C
7
5a
5b
5c
6a
6b
6c
7a
7b
7c
P(C6H11)3 (0.11, 0.90)
(C6H5S)3In (0.20, 0.45)
toluene
PPh3 (0.24, 0.90)
(C6H5S)3In (0.20, 0.45)
toluene
PEt3 (0.10, 0.83)
(4-MeC6H4S)3In (0.20, 0.41)
benzene
P(C6H11)3 (0.18, 0.83)
(4-MeC6H4S)3In (0.20, 0.41)
benzene
PPh3 (0.22, 0.83)
(4-MeC6H4S)3In (0.20, 0.41)
methanol
PEt3 (0.095, 0.81)
(4-FC6H4S)3In (0.20, 0.40)
toluene
P(C6H11)3 (0.11, 0.40)
(4-FC6H4S)3In (0.20, 0.40)
toluene
PPh3 (0.11, 0.40)
(4-FC6H4S)3In (0.20, 0.40)
toluene
2 day at 23 °C
12 h at 23 °C
0.21, 0.30, 66
0.089, 0.13, 28
0.092, 0.16, 38
0.19, 0.24, 59
0.11, 0.15, 36
0.13, 0.20, 51
0.27, 0.36, 89
0.28, 0.37, 93
C: [59.82 (59.97)]
H: [6.71 (7.07)]
130
88
C: [61.44 (61.52)]
H: [4.30 (4.21)]
layered with hexane
1 h at 23 °C
C: [53.80 (53.72)]
H: [6.03 (6.11)]
118
110
122
111
104
123
layered with hexane
2 d at 23 °C
C: [61.20 (61.70)]
H: [7.13 (7.31)]
2 d at 23 °C
C: [62.70 (62.55)]
H: [4.87 (4.53)]
layered with hexane
1 h at 23 °C
pumped to dryness
pumped to dryness
a N < 0.5% for all compounds.
Preparation of (4-RC6H4S)In‚PR′3 [R ) H, R′ ) Et (5a), Cy
(5b), Ph (5c); R ) Me, R′ ) Et (6a), Cy (6b), Ph (6c); R ) F,
R′ ) Et (7a), Cy (7b), Ph (7c)]. A solution of PR′3 in benzene,
toluene, or methanol (2 mL) was added dropwise to a mixture of
5-7 in the same solvent (3 mL) at 23 °C. After 2 h, the clear
solution was decanted and the volume decreased to 0.5 mL. The
product was then layered with hexane (0.5 mL) or allowed to slowly
evaporate to yield colorless crystals. For the preparation of
compounds 7b and 7c, the reaction mixture was pumped to dryness
to yield a white powder of the desired product. Despite several
attempts, satisfactory elemental analysis could not be obtained for
7a-c.
X-Ray Structural Analyses. Crystals of 5c, 6a, and 7a were
isolated from the reaction mixtures as indicated above. Crystals of
6c‚MeOH‚H2O were isolated from the 1:2 reaction of (4-MeC6H4S)3-
In and PPh3 in methanol in air. Single crystals of 5c, 6a, 6c‚MeOH‚
H2O, and 7a were coated with Paratone-N oil, mounted using a
glass fiber, and frozen in the cold nitrogen stream of the goniometer.
A hemisphere of data was collected on a Bruker AXS P4/SMART
1000 diffractometer using ω and θ scans with a scan width of 0.3°
and exposure times of 10 (5c, 7a), 30 (6a), or 40 s (6c‚MeOH‚
H2O). The detector distance was 5 cm. The data were reduced
(SAINT)13 and corrected for absorption (SADABS).14 The structures
were solved by direct methods and refined by full-matrix least
squares on F2 (SHELXTL).15 All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were found in Fourier difference
maps and refined isotropically (7a) or were included in calculated
positions and refined using a riding model (5c, 6a, and 6c‚MeOH‚
H2O). Due to a disorder in the phenylthiolate groups in 5a, a
satisfactory refinement of the structure could not be obtained.
[Crystal data for 5a: C24H30InPS3, fw ) 560.45, trigonal, space
group P31c, a ) 13.9347(18) Å, c ) 7.7828(12) Å, V ) 1308.8-
(3) Å3, Z ) 2].
Results and Discussion
Syntheses. The aryl disulfides (4-RC6H4S)2 (R ) H, Me,
F) were prepared in high yield by oxidation of the corre-
sponding aryl thiol with 30% H2O2 in methanol or water.
The 2:3 reaction of indium powder with the corresponding
aryl disulfide in methanol under reflux gives (4-RC6H4S)3In
[R ) H (5), Me (6), F (7)] in high yield (82-95%) after
removal of the solvent in vacuo. A slight modification of
this synthetic method has been employed previously to
prepare 5.7
Reaction of 5-7 with the tertiary phosphines PR′3 [R′ )
Et (a), Cy (b), Ph (c)] in benzene or toluene resulted in the
formation of the 1:1 adducts (4-RC6H4S)In‚PR′3 (5a-c, 6a-
c, 7a-c) in moderate yields (see Table 1). Addition of the
phosphine solution to a slurry of the insoluble indium thiolate
gave a clear solution after stirring for a few minutes at room
temperature, indicating the adduct is readily formed. Interest-
ingly, a 1:2 reaction stoichiometry results in isolation of
crystals of the 1:1 adducts only (5a-c, 6a-c, 7a). As 7b
and 7c were isolated as powders after the removal of solvent
from the reaction mixture, a 1:1 reaction stoichiometry was
(13) SAINT 6.02; Bruker AXS, Inc.: Madison, WI, 1997-1999.
(14) Sheldrick, G. SADABS; Bruker AXS, Inc.: Madison, WI, 1999.
(15) Sheldrick, G. SHELXTL 5.1; Bruker AXS, Inc.: Madison, WI, 1997.
9916 Inorganic Chemistry, Vol. 44, No. 26, 2005

Substituent Effects on Indium-Phosphorus Bonding
Table 2. Vibrational Bands and NMR Data
NMR (ppm)b
a
a
compound
FT-IR (cm-1
)
FT-Raman (cm-1
)
1H
31P{1H}
5
669m, 731m, 825w,
877s, 1099w, 1252m,
1643m, 2359s
119m, 161s, 281w, 325w,
392m, 491w, 628s, 638w
6.99 (m, 9H, H5C6S)
7.28 (m, 6H, H5C6S)
6
721s, 798vs, 877w,
1016s, 1084m, 1184w,
1633m
513s, 625s, 762s, 827vs,
877m, 1159s, 1234vs,
1296w, 1587s
97m, 134w, 177vs, 253m,
314m, 426s, 616m, 694m
2.22 (s, 9H, 4-MeH4C6S)
6.82 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
7.17 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
6.51 (m, 6H, 4-FH4C6S)
7
116s, 160s, 208w, 229m,
292s, 319w, 352m, 389s,
420w, 511w, 626s
6.71 (m, 6H, 4-FH4C6S)
5a
5b
692vs, 739vs, 769s,
1022m, 1082m,
1261m, 1574s
850m, 1020m, 1114m,
1261m, 1296m, 1572w
110s, 226w, 285m, 335m,
388m, 628m
0.56-1.00 (m, 15H, PEt3)
6.84-7.00 (m, 9H, H5C6S)
7.76-7.79 (m, 6H, H5C6S)
1.00-1.93 (m, 33H, PCy)
6.89 (t, 3JH,H ) 9 Hz, 3H, H5C6S)
7.01 (m, 6H, H5C6S)
-5.3
105s, 247w, 285w
19.8
7.81 (d, 3JH,H ) 7 Hz, 6H, H5C6S)
6.85-6.88 (m, 9H, H5C6S)
6.96-7.02 (m, 9H, PPh3)
5c
6a
6b
6c
694vs, 742vs, 877w,
1024s, 1080s, 1153m,
1576s
103s, 196w, 214w, 253m
-4.2
-2.0
19.7
7.26-7.33 (m, 6H, PPh3)
7.48-7.51 (m, 6H, H5C6S)
0.58-1.16 (m, 15H, PEt3)
2.01 (s, 9H, 4-MeH4C6S)
498s, 627m, 812vs,
876w, 1043m, 1088vs,
1210w, 1267m, 1595w
116s, 160vs, 209w, 230m,
292s, 319w, 352m, 389s,
421w, 510w, 626s
6.81 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
7.73 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
1.02-1.96 (m, 33H, PCy3)
2.03 (s, 9H, 4-MeH4C6S)
721s, 808s, 877m,
1020s, 1086m, 1261m,
1621s, 2727w
145w, 245m, 273m, 341m,
384m, 687w
6.85 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
7.77 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
1.96 (s, 9H, 4-MeH4C6S)
694s, 721s, 741m,
800s, 1026s, 1086s,
1261s, 1621m
93m, 111m, 189m, 262m,
322m, 421w
-4.2
6.72 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
6.97 (d, 3JH,H ) 8 Hz, 6H, 4-MeH4C6S)
7.00-7.06 (m, 9H, PPh3)
7.32-7.42 (m, 6H, PPh3)
7a
723s, 804m, 876w,
1018m, 1084m,
1153w, 1223w,
113s, 188s, 262s, 324s,
420m, 616m, 695m
0.51-0.67 (m, 9H, PEt3)
-0.46
0.88-0.94 (m, 6H, PEt3)
6.63 (m, 6H, 4-FH4C6S)
1261m, 1601m
7.49 (m, 6H, 4-FH4C6S)
7b
7c
509m, 627s, 721m,
827s, 877m, 1083s,
1155w, 1223s, 1585m
505s, 627s, 694vs,
742vs, 823vs, 876w,
1012w, 1084m,
94w, 142m, 180w, 228m,
246w, 295s, 307w, 363m,
379w, 388w, 629m
100w, 157w, 193m, 218m,
249m, 276w, 290m, 324w,
359s, 381w, 368w, 420w,
521w, 618w, 626m, 687w
0.94-1.99 (m, 33H, PCy3)
22.2
6.65 (m, 6H, 4-FH4C6S)
7.59 (m, 6H, 4-FH4C6S)
6.51 (m, 6H, 4-FH4C6S)
6.71 (m, 6H,4-FH4C6S)
6.85-7.01 (m, 6H, PPh3)
7.34-7.44 (m, 9H, PPh3)
-3.4
1157m, 1228s, 1587s
a Vibrational bands below 1600 cm-1 b Methanol-d4 (5-7), benzene-d6 (5a-c, 6a-c, 7a-c).
.
employed to prevent contamination with excess phosphine.
The complex (PhS)3In‚PCy3 (5b) has been reported previ-
ously but was prepared via reaction Ph2S2 with the indium
hydride adduct H3In‚(PCy3)2.12 The adducts show no sign
of decomposition on standing in air for a period of days.
Further, these shifts are inversely proportional to the observed
In-P bond distances (vide infra). Finally, 31P{1H} spectra
of reaction mixtures show no indication of the formation of
1:2 indium thiolate-phosphine adducts in solution.
Crystallographic Analyses. Crystals suitable for X-ray
crystallographic analysis were isolated for 5a-c, 6a, 6c, and
7a from the slow evaporation of reaction mixtures at 23 °C.
Crystallographic data are given in Table 3. Selected bond
distances and angles are given in Table 4. Due to a disorder
in the phenylthiolate groups in 5a, a satisfactory refinement
of the structure could not be obtained. However, useful
preliminary data regarding the indium-phosphorus bonding
interaction are discernible. The structure of 5b has been
reported previously.12
Representative structures of (4-RC6H4S)3In‚PR′3 adducts,
indicating atom numbering schemes, are shown in Figures
1 (6c) and 2 (7a). Compounds 5a and 6c crystallize in a
hexagonal space group, resulting in a 3-fold symmetry in
the complex in each case. All structures show 1:1 tris-
(arylthiolato)indium-triorganylphosphine complexes, facili-
1
Solution NMR studies. Solution H, 13C{1H}, and 19F
(7a-c) resonances of all indium thiolate-phosphine com-
plexes (see Table 2 and Supporting Information) show slight
changes in frequency compared to the phosphine reactants
(a-c) in the same solvents. Particularly diagnostic, however,
are the 31P{1H} resonances, which show a downfield shift
for the indium-phosphine adducts versus the uncoordinated
phosphine in the same solvent (PEt3, -18.7; PCy3, 10.9;
PPh3, -4.8 ppm). Interestingly, these shifts are largest for
the PEt3 adducts 5-7a (13.4-18.2 ppm), smaller for the
PCy3 adducts 5-7b (8.8-11.3 ppm), and only very slight
for the PPh3 adducts 5-7c (0.6-1.4 ppm). These data
suggest that the indium-phosphorus bonding interaction is
resilient on dissolution of the adducts in weakly coordinating
benzene-d6 and is influenced by the phosphine substituents.
Inorganic Chemistry, Vol. 44, No. 26, 2005 9917

Briand et al.
Table 3. Crystallographic Data for 5c, 6a, 6c‚MeOH‚H2O, and 7a
5c
6a
6c‚MeOH‚H2O
7a
formula
fw
crystal system
space group
a (Å)
C36H30InPS3
704.57
triclinic
P1h
9.8480(9)
10.4722(10)
16.0178(14)
94.764(2)
92.905(2)
105.299(2)
1583.3(3)
2
C27H36InPS3
602.53
orthorhombic
Pna2(1)
25.3684(14)
7.8320(5)
14.3950(8)
90
90
90
2860.1(3)
4
C45H62InO7PS3
956.92
trigonal
P31c
14.8616(10)
14.8616(10)
12.2118(10)
90
90
120
2335.8(3)
2
C24H27F3InPS3
614.43
monoclinic
P2(1)/n
7.8904(3)
24.3493(10)
13.7357(5)
90
94.428(1)
90
2631.10(18)
4
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
F(000)
716
1.478
1.019
198(1)
0.71073
0.0458
0.1176
1240
1.399
1.115
198(1)
0.71073
0.0308
0.0726
1000
1.361
0.721
198(1)
0.71073
0.0292
0.0714
1240
1.551
1.229
198(1)
0.71073
0.0251
0.0609
F
calcd, g cm-3
µ, mm-1
T, K
λ, Å
R1a
wR2b
a R1 ) [∑ ||Fo| - |Fc||]/[∑ |Fo|] for [Fo > 2σ(Fo )]. b wR2 ) {[∑ w(Fo - Fc )2]/[∑ w(Fo )]}1/2
.
2
2
2
2
4
Table 4. Selected Bond Distances (Å) and Angles (deg) for 5b, 5c, 6a, 6c‚MeOH‚H2O, and 7a
5b12
5c
6a
6c‚MeOH‚H2O
7a
In-P
2.6109(8)
2.4456(10)
2.4544(9)
2.4384(9)
1.843(1)
2.6458(12)
2.4323(12)
2.4333(13)
2.4252(14)
1.811(5)
2.5881(9)
2.4434(12)
2.4404(11)
2.4434(10)
1.806(7)
2.6493(12)
2.4286(8)
2.5840(5)
2.4538(6)
2.4363(6)
2.4446(6)
1.823(2)
1.825(2)
1.819(2)
In-S(1)
In-S(2)
In-S(3)
P-C(11)
P-C(21)
P-C(31)
1.810(3)
1.846(1)
1.840(1)
1.797(4)
1.805(4)
1.835(6)
1.818(4)
S(1)-In-S(2)/S(1′)
S(1)-In-S(3)
109.48(3)
121.27(5)
115.07(4)
112.206(18)
107.28(10)
114.72(2)
119.96(4)
105.79(4)
108.12(14)
105.97(13)
110.90(14)
115.02(5)
107.70(5)
106.6(2)
106.8(2)
106.5(2)
109.06(4)
111.85(4)
107.3(4)
105.5(3)
106.5(3)
111.48(2)
112.55(2)
106.14(12)
106.74(12)
107.79 (12)
S(2)-In-S(3)
C(11)-P-C(21)/C(11′)
C(11)-P-C(31)
C(21)-P-C(31)
tated via indium-phosphorus bonding interactions. This
results in a four-coordinate, distorted tetrahedral bonding
environment for both indium and phosphorus. The In-S
distances [2.4252(14)-2.4560(6) Å] are similar to those of
the known (C6H5S)3In‚P(Cy)3 (5b)12 and fall in the range
observed for other neutral indium thiolate adducts [2.410-
(2)-2.472(3) Å].4b,5b,6 The In-P bond distances for the PEt3
(5-7a) and PCy3 (5b) adducts are similar to those of
previously reported 1:1 InI3-phosphine adducts [2.586(6)-
2.616(9) Å],9,10a while the corresponding distances for the
PPh3 adducts (5c and 6c) are significantly longer. This is
presumably an electronic versus a steric effect, as PPh3 has
the poorest electron donor ability of the three phosphines
studied but has an intermediate cone angle (PEt3 < PPh3 <
PCy3).16 Interestingly, a comparison of the In-P bond
distances in 5a-c shows that they are all significantly
different and increase in the order 5a [2.569(5) Å] < 5b
[2.6109(8) Å] < 5c [2.6458(12) Å]. Comparison of the In-P
bond distances for the three PEt3 derivatives (5-7a) shows
that the values for 5a and 6a [2.5881(9) Å] are significantly
different. However, distances for the PPh3 derivatives 5c and
6c are within experimental error. These data suggest that
the phosphine substituents (a-c) significantly influence the
Figure 1. X-ray structure of 6c (30% probability ellipsoids). Hydrogen
atoms are removed for clarity. Symmetry transformations used to generate
equivalent atoms: (′) 1 - y, 1 + x - y, z; (′′) -x + y, 1 - x, z.
Figure 2. X-ray structure of 7a (30% probability ellipsoids). Hydrogen
atoms are removed for clarity.
9918 Inorganic Chemistry, Vol. 44, No. 26, 2005

Substituent Effects on Indium-Phosphorus Bonding
Figure 3. (a) Thermogravimetric analysis and (b) differential scanning
calorimetry measurements for (C6H5S)3In‚PPh3 (5c).
In-P bond distance, while the 4-substituted phenylthiolate
groups on indium (5-7) have a negligible effect. Comparison
of the sum of S-In-S bond angles of 5a-c, 6a-c, and
7a-c shows a range of 333.9(2)-343.99(5)°, with no
correlation to the corresponding In-P bond distances.
Thermal Decomposition Analyses. Compounds 5a-c,
6a-c, and 7a-c were found to have sharp melting points
in the range of 88-130 °C. The low melting points are
interesting given that the tris(arylthiolato)indium reactants
(5-7) thermally decompose above 300 °C without melting.
This is a result of the monomeric nature of the indium-
phosphine adduct, as compared to the presumably polymeric
structure of uncomplexed homoleptic indium tris(arylthio-
lates).4,6
To examine the properties of the indium thiolate-
phosphine adducts on heating, TGA and DSC data were
collected under dinitrogen atmosphere in the temperature
range 30-600 °C using a heating rate of 10 °C/min. The
respective plots for (PhS)3In‚PPh3 (5c) are shown in Figure
3. The DSC trace shows an endothermic process up to 78
°C (temperature range A), which is near the melting point
of the compound. Minimal mass loss (2-3%) is observed
in the TGA profile in this temperature range but is followed
by significant mass loss in two distinct stages (temperature
range B). The first stage ends at ∼285 °C (55% mass
remaining), and the second at 395 °C (20% mass remaining).
These mass losses are accompanied by two endothermic
features in the DSC plot. There is minimal mass loss above
∼390 °C (temperature range C), with 17% mass remaining
at 600 °C. This corresponds to the mass percent of indium
in the compound (16%). The DSC plot shows a second
endothermic process in this temperature range.
Figure 4. (a) Temperature programmed EI-MS ion flux trace for (C6H5S)3-
In‚PPh3 (5c); (b) mass spectrum at 12.5 min (230 °C) showing PPh3
fragments; and (c) mass spectrum at 18.7 min (300 °C) showing phenylthi-
olate ligand fragments.
40-300 °C is shown in Figure 4a. Here, the number of ions
in the gas phase is negligible below the melting point, then
begins to increase exponentially on further temperature
elevation. Analysis of the mass spectrum at maximum ion
flux (230 °C; Figure 4b) shows ions characteristic of PPh3
(m/z 183, [PPh2]•+; m/z 262, [PPh3]•+; m/z 445, [PPh3‚
PPh2]•+). The ion flux then decreases rapidly until ∼16 min
(300 °C). On being held at 300 °C, there is a second rapid
increase in ion formation. Analysis of the mass spectrum at
18.6 min (Figure 4c) shows ions resulting from the phenyl
thiolate ligand (m/z 110, [PhSH]•+; m/z 218, [(PhS)2]•+). The
molecular ion [(4-RC6H4S)In‚PR′3]•+ was not observed in
the spectra of any of the adducts.
Taken together, the DSC/TGA and EI-MS data suggest
that 5c thermally decomposes through an initial loss of the
phosphine moiety (PPh3) in the 78-285 °C temperature
range. As the PPh3 moiety constitutes only 37% mass of the
compound, the loss of 45% mass in the TGA data suggests
some thiolate ligand is also expunged in this step. This is
followed by loss of the majority of thiolate ligand (SPh) in
the 285-390 °C temperature range. Loss of the residual
thiolate ligand occurs above 390 °C, presumably yielding
elemental indium as the final product of decomposition at
600 °C.
The DSC/TGA data and EI-MS ion trace for the remaining
adducts (see Supporting Information) suggest similar thermal
decomposition pathways. However, a complete loss of
phosphine and thiolate ligand is observed for 6b only (15%
mass In; 13% residual mass). Although a loss of some
phosphine and thiolate ligand is observed in all cases, TGA
To aid in the interpretation of these results, electron impact
mass spectrometric (EI-MS) analyses were performed on all
adducts. The ion flux trace for 5c over the temperature range
(16) Tolman, C. A. Chem. ReV. 1977, 77, 313-348.
Inorganic Chemistry, Vol. 44, No. 26, 2005 9919

Briand et al.
data show residual masses of 13-51%, while indium
constitutes only 15-20% of the total mass of all adducts.
This suggests that the loss of ligand is not complete at 600
°C, and the remaining residue likely contains a significant
amount of ligand material.
ing an initial loss of the phosphine moiety followed by loss
of thiolate ligand. These losses are complete in some cases,
yielding elemental indium as the final product of decomposi-
tion. These results suggest that, although the phosphine
substituents significantly affect the strength of the indium
phosphorus Lewis acid-base interaction, the bond is too
labile to allow for the thermal vaporization of these adducts.
Therefore, these compounds are not suitable precursors for
the production of InP via thermal decomposition methods.
We are currently investigating the thermal decomposition
properties of other molecular species incorporating indium-
phosphorus bonding interactions.
Conclusions
The series of indium-phosphine adducts (4-RC6H4S)3In‚
PR′3 [R ) H, R′ ) Et (5a), Cy (5b), Ph (5c); R ) Me, R′
) Et (6a), Cy (6b), Ph (6c); R ) F, R′ ) Et (7a), Cy (7b),
Ph (7c)] were prepared from the reaction of the appropriate
tris(arylthiolate)indium(III) and triorganylphosphine reactants
to determine the effect of the thiolate and phosphine
substituents on their spectroscopic, structural, and thermal
decomposition properties. The X-ray structures of 5c, 6a,
6c, and 7a show monomeric 1:1 adduct complexes in all
cases. The In-P bond distances were found to be influenced
by the phosphine substituents (PEt3 < PCy3 < PPh3) but
not by the 4-substituted phenylthiolate ligand. Solution 31P-
{1H} spectra show retention of the In-P bond in benzene-
d6 solution. The phosphine signals are shifted downfield
versus the free ligand, the degree of which is inversely
proportional to the In-P bond distance. Relatively low
melting points were observed for all adducts due to the
monomeric nature of the adducts, versus the high-temperature
thermal decomposition observed for the polymeric parent
indium thiolates (4-RC6H4S)3In (5-7). EI-MS and DSC/TGA
data show a two-step thermal decomposition process, involv-
Acknowledgment. We thank the following. Dan Durant
for assistance in collecting NMR data, Dr. Stephen Duffy
for assistance in collecting mass spectrometry data, the
Department of Chemistry, Dalhousie University for FT-
Raman spectrometer access, Dr. Jeff Dahn (Dalhousie
University) for DSC/TGA data, and the Natural Sciences and
Engineering Research Council of Canada, the New Bruns-
wick Innovation Foundation and Mount Allison University
for financial support.
Supporting Information Available: X-ray crystallographic data
for 5c, 6a, 6c‚MeOH‚H2O, and 7a; 13C{1H} and 19F NMR, DSC/
TGA and EI-MS data for 5a-c, 6a-c, and 7a-c. This material is
available free of charge via the Internet at http://pubs.acs.org.
IC051138R
9920 Inorganic Chemistry, Vol. 44, No. 26, 2005